2001 Subaru Outback car problem

I can get you part way through the diagnosis. First of all, that fat output wire that's bolted on must have 12 volts all the time when the engine is not running. If it has 0 volts, look for a blown very large fuse. That could be a 100 amp fuse that's bolted into the fuse box. If you have a fuse link wire instead of a fuse, you test them by tugging on them. If it acts like a wire, it's good. If it's bad it will act like a rubber band.

Next, look at the three wires in the plug. The middle one must also have 12 volts but that might not be there unless the ignition switch is on. If that is missing, check the fuses. Of the last two wires in that plug, one is ground and will always have 0 volts, and the other one runs the dash light. That is the turn-on signal for the generator. If the dash light turns on, that circuit should be okay, but check the voltage on that wire anyway. Expect to find only about 2 volts when you back-probe that wire through the connector. It has to be plugged in for that reading to be accurate.